Method for retransmitting data in the multi-carrier system

ABSTRACT

A method for modifying a synchronous non-adaptive retransmission scheme to solve the limitation of the synchronous non-adaptive retransmission scheme is disclosed. A method for indicating not only the new data transmission but also the retransmission using a data scheduling message is disclosed. A method for determining whether there is an error in the ACK signal transmitted from a data reception end using another message to -be received later is disclosed. The retransmission method for a multi-carrier system includes: receiving a grant message including scheduling information for transmitting uplink data wherein a retransmission scheme for the uplink data is predetermined by a first retransmission scheduling, transmitting the uplink data according to the scheduling information and retransmitting the uplink data according to second retransmission scheduling by receiving the second retransmission scheduling information associated with the uplink data with retransmission request.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/443,970, filed Mar. 12, 2010, currently pending, which is theNational Stage filing under 35 U.S.C. 371 of International ApplicationNo. PCT/KR2007/004831, filed on Oct. 2, 2007, which claims the priorityof Provisional Application Nos. 60/827,858, filed Oct. 2, 2006 and60/944,791, filed Jun. 18, 2007, and Korean Patent Application Nos.10-2007-0001215, filed Jan. 5, 2007 and 10-2007-0099052, filed Oct. 2,2007, the contents of which are hereby incorporated by reference hereinin their entirety.

TECHNICAL FIELD

The present invention relates to a multi-carrier system, and moreparticularly to a retransmission method for use in the multi-carriersystem.

BACKGROUND ART

A mobile communication system allows each base station or Node-B locatedin a single cell or sector to communicating with a plurality of userterminals (e.g., user equipments) over a wireless channel environment.

In the case of a multi-carrier system or other systems similar to themulti-carrier system, the base station receives packet traffic from awired Internet network in the multi-carrier system or other similarsystems, and transmits the received packet traffic to each terminalusing a predetermined communication scheme.

In this case, the base station determines a downlink scheduling, so thatit determines a variety of information according to the downlinkscheduling, for example, a user terminal which will receive data fromthe base station, a frequency area to be used for data transmission tothe terminal, and timing information indicating a transmission time ofthe data to be transmitted to the terminal.

The base station receives packet traffic from the user terminalaccording to a predetermined communication scheme, and demodulates thereceived packet traffic, so that it transmits the received packettraffic to the wired Internet network.

The base station determines an uplink scheduling, so that it determinesa variety of information according to the uplink scheduling, forexample, a user terminal which will transmit uplink data, a frequencyband to be used for the uplink data transmission, and timing informationindicating a transmission time of the uplink data. Generally, a userterminal having a superior or good channel status is scheduled totransmit/receive data using more frequency resources during a longertime.

FIG. 1 is a conceptual diagram illustrating a time-frequency resourceblock for use in a multi-carrier system.

Communication resources for use in a multi-carrier system or othersimilar systems can be largely divided into a time area and a frequencyarea.

The communication resources can be defined by resource blocks. Eachresource block includes N sub-carriers and/or M sub-frames, and isconfigured in units of a predetermined time. In this case, N may be setto “1”, and M may also be set to “1”.

A single square of FIG. 1 indicates a single resource block. A singleresource block uses several sub-carriers as a single axis, and uses aunit of a predetermined time as another axis.

A base station in a downlink selects a user terminal according to apredetermined scheduling rule, allocates one or more resource blocks tothe selected user terminal. The base station transmits data to theselected user terminal using the allocated resource blocks.

According to uplink transmission, the base station selects the userterminal, and allocates one or more resource blocks to the selected userterminal according to a predetermined scheduling rule. The user terminalreceives scheduling information, indicating that a predeterminedresource block has been allocated to the user terminal itself, from thebase station, and transmits uplink data using the allocated resource.

Although data has been transmitted according to the scheduling rule, thedata may be unexpectedly damaged or lost during the transmissionprocess. In this case, there are proposed a variety method forcontrolling the faulty or erroneous operation, for example, an automaticrepeat request (ARQ) scheme and a hybrid ARQ (HARQ) scheme, etc. Theconfirmation of the faulty or erroneous operation according to theabove-mentioned two schemes is operated in frame units. Data transmittedduring the frame unit is hereinafter referred to as a frame.

The ARQ scheme waits for transmission of the ACK signal aftertransmitting a single frame. If a reception end correctly receives dataof the frame, it transmits the ACK signal. However, if an unexpectederror occurs in the frame, the reception end transmits a negative-ACK(NACK) signal, and deletes the received erroneous frame from its ownbuffer.

If the transmission end receives the ACK signal, it transmits the nextframe. Otherwise, if the transmission end receives the NACK signal, itretransmits the frame.

The HARQ scheme allows the reception end to transmit the NACK signal tothe transmission end on the condition that the received frame cannot bedemodulated. However, differently from the ARQ scheme, the HARQ schemedoes not delete the pre-received frame from the buffer, and stores thepre-received frame in the buffer for a predetermined period of time.Therefore, if the above-mentioned frame is re-transmitted, in the HARQscheme the reception end combines the pre-received frame with are-transmitted frame, thereby it could increase the success rate of datareception.

In recent time, many users prefer to the HARQ scheme to the basic ARQscheme.

There are a variety of types in the HARQ scheme. For example, the HARQscheme can be classified into a synchronous HARQ scheme and anasynchronous HARQ scheme.

If initial transmission of data fails, the synchronous HARQ scheme isdesigned to perform the next retransmission of data at a timing pointdetermined by a system. For example, if it is assumed that theretransmission timing point is set to a fourth time unit after theinitial transmission failure occurs, there is no need to additionallyindicate the fourth time unit because the retransmission timing betweenthe base station and the user terminal is pre-engaged.

In other words, if the transmission end of data receives the NACKsignal, it re-transmits the frame every fourth time unit until receivingthe ACK signal.

In the meantime, the asynchronous HARQ scheme is performed by thenewly-scheduled retransmission timing and the additional signaltransmission. In other words, a timing point at which thepreviously-failed frame is re-transmitted is variable with a variety offactors such as a channel status.

The HARQ scheme can be classified into a channel-adaptive HARQ schemeand a channel-non-adaptive scheme according to information indicatingwhether a channel status is reflected in allocation of resources usedfor retransmission.

The channel-non-adaptive HARQ scheme (also called a non-adaptive HARQscheme) enables resource blocks used for retransmission, and a MCS(Modulation and Coding Scheme) level defining frame modulation andcoding methods to be operated according to a specific schemepredetermined by initial transmission.

The channel-adaptive scheme (also called an adaptive HARQ scheme) allowsthe above-mentioned resource blocks and the MCS level to be variablewith channels status information.

For example, according to the channel-non-adaptive HARQ scheme, atransmission end transmits data using eight resource blocks during theinitial transmission, and then re-transmits the data using the sameeight resource blocks irrespective of a channel status acquired byretransmission of the data.

On the other hand, according to the channel-adaptive HARQ scheme,although data is initially transmitted using 8 resource blocks, the datamay also be re-transmitted using eight or less resource blocks or eightor more resource blocks according to the next channel status asnecessary.

According to the above-mentioned classification, the HARQ scheme mayhave four combinations of the HARQ schemes. According to uniquecharacteristics of the above-mentioned schemes, the most preferredcombinations of the HARQ schemes are an asynchronous channel-adaptiveHARQ scheme, and a synchronous channel-non-adaptive scheme.

Generally, the asynchronous channel-adaptive HARQ scheme adaptivelychanges a retransmission timing point and the amount of used resourcesto others according to a channel status, so that it can maximize theretransmission efficiency. In the meantime, the synchronouschannel-non-adaptive HARQ scheme has an advantage in that there isalmost no overhead because the retransmission timing and the resourceallocation for retransmission are pre-engaged in a system.

DISCLOSURE Technical Problem

However, the above-mentioned asynchronous channel-adaptive HARQ schemehas a disadvantage in that it unavoidably increases an amount ofoverhead, so that it is not generally considered for an uplink. And ifthe synchronous channel-non-adaptive HARQ scheme is used under anexcessively-changing channel status, retransmission efficiency isexcessively decreased.

Technical Solution

Accordingly, the present invention is directed to a retransmissionmethod for use in a multi-carrier system that substantially obviates oneor more problems due to limitations and disadvantages of the relatedart.

An object of the present invention is to provide a retransmission methodin a multi-carrier system.

Another object of the present invention is to provide a method forindicating a retransmission request via an uplink scheduling message ina multi-carrier system.

Another object of the present invention is to provide a method fordetermining whether there is an erroneous or faulty in an ACK/NACKsignal at a reception end of the ACK/NACK signal.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, aretransmission method for a multi-carrier system comprising: receiving agrant message including scheduling information for transmitting uplinkdata wherein a retransmission scheme for the uplink data ispredetermined by a first retransmission scheduling, transmitting theuplink data according to the scheduling information, and retransmittingthe uplink data according to second retransmission scheduling byreceiving the second retransmission scheduling information associatedwith the uplink data with retransmission request.

The second retransmission scheduling information may include changedinformation of at least one of a retransmission timing, retransmissionresource blocks, a number of the retransmission resource blocks, and atransmission format of retransmission the second retransmissionscheduling information with comparing with the first retransmissionscheduling.

In another aspect of the present invention, there is provided aretransmission method for a multi-carrier system comprising: receiving agrant message including scheduling information for transmitting uplinkdata, transmitting the uplink data according to the schedulinginformation, receiving a grant message indicating a retransmission ofthe uplink data, and retransmitting the uplink data.

The grant message may include information indicating one of new datatransmission and retransmission.

The information indicating one of the new data transmission and theretransmission may apply a toggling scheme to change a current value ofthe information to another value if the new data transmission isindicated.

The information indicating one of the new data transmission and theretransmission may be initialized if the new data transmission isindicated, or be changed according to a predetermined rule if theretransmission is indicated.

If a retransmission scheme for the uplink data is predetermined by afirst retransmission scheduling and the grant message indicating theretransmission includes second retransmission scheduling information,the retransmission may be performed according to the secondretransmission scheduling information.

In yet another aspect of the present invention, there is provided aretransmission method for a multi-carrier system comprising:transmitting data, receiving an acknowledgement signal of the data; anddetermining whether an error occurs in the acknowledgement signal byreferring to a scheduling message received after the acknowledgementsignal.

The method may further comprise: maintaining the data in a buffer evenwhen the received acknowledgement signal is an affirmativeacknowledgement (ACK) signal.

Provided that the acknowledgement signal is the affirmativeacknowledgement (ACK) signal, if the scheduling message indicates newdata transmission, it may be determined that the acknowledgement signalhas no error; and if the scheduling message indicates retransmission, itmay be determined that the acknowledgement signal has an error.

In yet another aspect of the present invention, there is provided aretransmission method for a multi-carrier system comprising:transmitting data, receiving an acknowledgement signal of the data, andmaintaining the data in a buffer until receiving a scheduling message.

The method may further comprise: if the scheduling message indicates anew data transmission, deleting the data from the buffer, andtransmitting new data; and if the scheduling message indicates aretransmission, retransmitting the data.

The acknowledgement signal may be at least one of an affirmativeacknowledgement signal, a stop message, and a grant message.

The grant message may include information indicating that there is noresource block allocated for the data retransmission.

The acknowledgement signal may be transmitted to interrupt theretransmission if resources for retransmission data cannot be allocatedat a predetermined retransmission timing of the data.

The data may not be retransmitted at the predetermined retransmissiontiming, and is then retransmitted at the next retransmission timing.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

If the retransmission method for the multi-carrier system is based on achannel-non-adaptive retransmission scheme, the present invention canflexibly or smoothly schedule retransmission resources.

If the retransmission method for the multi-carrier system is based on asynchronous retransmission scheme, the present invention can flexibly orsmoothly schedule the retransmission timing point.

Also, the present invention can more effectively perform the synchronouschannel-non-adaptive HARQ scheme.

The present invention can properly cope with the ACK/NACK errors, sothat a communication performance increases.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

In the drawings:

FIG. 1 is a conceptual diagram illustrating a time-frequency resourceblock used for the scheduling of a multi-carrier system;

FIG. 2 is a conceptual diagram illustrating a general synchronouschannel-non-adaptive HARQ scheme capable of being applied to an uplinktransmission;

FIG. 3 is a conceptual diagram illustrating a retransmission method foruse in a multi-carrier system according to an embodiment of the presentinvention;

FIG. 4 is a conceptual diagram illustrating a retransmission method foruse in a multi-carrier system according to another embodiment of thepresent invention;

FIG. 5 is a conceptual diagram illustrating a method for informing thata grant message indicating which one of new data transmission andretransmission is requested in case that the grant message is used forrequesting retransmission according to another embodiment of the presentinvention;

FIG. 6 is a conceptual diagram illustrating another method for informingthat a grant message indicating which one of new data transmission andretransmission is requested in case that the grant message is used forrequesting retransmission according to another embodiment of the presentinvention;

FIG. 7 is a conceptual diagram illustrating another method for informingthat a grant message indicating which one of new data transmission andretransmission is requested in case that the grant message is used forrequesting retransmission according to another embodiment of the presentinvention;

FIG. 8 is a conceptual diagram illustrating a method for indicating aretransmission stop according to an embodiment of the present invention;

FIG. 9 is a conceptual diagram illustrating a method for indicating aretransmission according to an embodiment of the present invention;

FIG. 10 is a conceptual diagram illustrating a method for transmitting aretransmission request message according to an embodiment of the presentinvention;

FIG. 11 is a conceptual diagram illustrating a method for simultaneouslyemploying the retransmission stop request message and the retransmissionrequest message according to an embodiment of the present invention;

FIG. 12 is a conceptual diagram illustrating a general NACK-to-ACKerror;

FIG. 13 is a conceptual diagram illustrating an exemplary method forapplying an embodiment of the present invention in consideration of theACK/NACK error;

FIG. 14 is a conceptual diagram illustrating another exemplary methodfor applying an embodiment of the present invention in consideration ofthe ACK/NACK error;

FIG. 15 is a conceptual diagram illustrating another exemplary methodfor applying an embodiment of the present invention in consideration ofthe ACK/NACK error; and

FIG. 16 is a conceptual diagram illustrating a method for controllingretransmission via the ACK/NACK message according to an embodiment ofthe present invention.

BEST MODE

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Prior to describing the present invention, it should be noted that mostterms disclosed in the present invention correspond to general termswell known in the art, but some terms have been selected by theapplicant as necessary and will hereinafter be disclosed in thefollowing description of the present invention. Therefore, it ispreferable that the terms defined by the applicant be understood on thebasis of their meanings in the present invention.

For the convenience of description and better understanding of thepresent invention, general structures and devices well known in the artwill be omitted or be denoted by a block diagram or a flow chart.Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts.

The following embodiments are proposed by combining constituentcomponents and characteristics of the present invention according to apredetermined format. The individual constituent components orcharacteristics should be considered to be optional factors on thecondition that there is no additional remark. If required, theindividual constituent components or characteristics may not be combinedwith other components or characteristics. Also, some constituentcomponents and/or characteristics may be combined to implement theembodiments of the present invention. The order of operations to bedisclosed in the embodiments of the present invention may be changed toanother Some components or characteristics of any embodiment may also beincluded in other embodiments, or may be replaced with those of theother embodiments as necessary.

The following embodiments of the present invention will be disclosed onthe basis of a data communication relationship between the Node-B andthe user equipment (UE). In this case, the Node-B is used as a terminalnode of a network via which the Node-B can directly communicate with theuser equipment (UE).

Specific operations to be operated by the Node-B in the presentinvention may also be operated by an upper node of the Node-B asnecessary. In other words, it will be obvious to those skilled in theart that various operations for enabling the Node-B to communicate withthe user equipment (UE) in a network composed of several network nodesincluding the Node-B will be operated by the Node-B or other networknodes other than the Node-B.

The term “Node-B” may be replaced with a fixed station, eNode-B (eNB),or an access point as necessary. The user equipment (UE) may also bereplaced with a mobile station (MS) or a mobile subscriber station (MSS)as necessary.

FIG. 2 is a conceptual diagram illustrating a general synchronouschannel-non-adaptive HARQ scheme capable of being applied to an uplinktransmission.

In the case of an uplink transmission, if the Node-B has a UE, whichwill transmit data to implement the UE's initial transmission, theNode-B informs the UE of wireless resource information and timinginformation to be used for the UE's data transmission, so that itgenerally transmits a scheduling message for allowing the UE's datatransmission to the UE. The above-mentioned scheduling message forallowing the UE's data transmission and informing scheduling informationis hereinafter referred to as a grant message.

The UE receives the grant message, acquires scheduling information, andtransmits data to the Node-B according to the acquired schedulinginformation.

In association with the transmitted (Tx) data, the UE normally receivesacknowledgment signal of the Tx data from the Node-B, so that it mayreceive the ACK signal from the Node-B or may also receive the NACKsignal requesting transmission of the data from the Node-B. If the UEreceives the ACK signal, it deletes the Tx data from a buffer, and waitsfor a transmission of new data. If the UE receives the NACK signal, itmay retransmit the Tx data according to a retransmission scheme.

In the case of data retransmission of a specific UE, which hastransmitted data to an uplink at a specific time according to thesynchronous channel-non-adaptive HARQ scheme, the retransmission timingis pre-engaged in a system. The resource block to be used for theretransmission and the transmission format are equal to those of theprevious transmission.

Therefore, it is sufficient that the grant message transmitted once fromthe Node-B should be transmitted to the UE for the initial transmission.The next retransmission may be operatedoperated by the ACK/NACK signalindicating whether data has been retransmitted or not without furtherinforming retransmission timing information and resource blocks to beused for the retransmission.

In the case of the synchronous channel-non-adaptive HARQ scheme, dataretransmission can be operatedoperated by transmission/reception of theNACK signal without using additional scheduling information between theNode-B and the UE. In other words, if the UE receives the NACK signalfrom the Node-B while maintaining the initially-transmitted data in itsown buffer, the UE can retransmit data using the same frequencyresources and MCS (Modulation and Coding Scheme) information as those ofthe initial transmission at a retransmission timing point having beenpredetermined before the retransmission.

However, in the case of maintaining characteristics of theabove-mentioned synchronous channel-non-adaptive HARQ scheme, acollision between the transmitted (Tx) data units may occur. In moredetail, if the retransmission is operatedoperated by the synchronouschannel-non-adaptive HARQ scheme, situation like that urgent data,high-priority control signals, or persistent scheduling data should betransmitted at predetermined retransmission timing using predeterminedretransmission resources can be occurred. In this case, if the UE, whichwill retransmit data using the synchronous channel-non-adaptive HARQscheme, retransmits the data using a corresponding resource at apre-engaged timing point, a collision between Tx data units of differentUEs may occur.

FIG. 3 is a conceptual diagram illustrating a retransmission method foruse in a multi-carrier system according to an embodiment of the presentinvention.

According to the embodiment of FIG. 3, the predetermined retransmissionscheduling can be changed in the synchronous channel-non-adaptive HARQscheme based multi-carrier system, and retransmission can be operatedaccording to the result of the changed retransmission scheduling.

For the convenience of description, it is assumed that the UEretransmits data via a second HARQ process in a 4-channel HARQ system, afirst data is transmitted at TTI=1, and the data cannot be retransmittedat TTI=9 which is a predetermined retransmission timing according to thesynchronous channel-non-adaptive HARQ scheme.

In this case, four HARQ processes having different retransmission timingpoints are defined in the 4-channel HARQ system, so that the 4-channelHARQ system allows the individual HARQ processes to perform theretransmission process during the same interval.

The aforementioned four HARQ processes are shown as index 0˜index 3respectively, in the center part of FIG. 3. That is, the index 0˜index 3in the center part of FIG. 3 is indicative of discriminatingretransmission timing information of the UE employing the first HARQprocess˜the fourth HARQ process, respectively.

For example, the UE scheduled to retransmit data by the second HARQprocess retransmits corresponding data at a timing of the first HARQprocess. In other words, the UE can retransmit the data at TTI=1, TTI=5,and TTI=9.

The Node-B transmits a grant message including scheduling information tothe uplink-scheduled UE. In this case, the scheduling informationinforms a scheduled frequency band at a scheduled Tx time theuplink-scheduled UE to transmit uplink data. If the UE receives thegrant message, the UE transmits data according to the schedulinginformation at the timing TTI=1.

The grant message may include a UE identifier (ID) for identifying acorresponding UE, resource block (RB) allocation information,information of transmittable data, payload information, and transmissionscheme information such as MCS (Modulation and Coding Scheme)information.

The RB allocation information may be set to the number of RBs to be usedby the above-mentioned UE, and/or the location information of the RBs.The above-mentioned transmittable data information may be set to thesize of data capable of being transmitted from the UE receiving thegrant message. The above-mentioned payload indicates a packet or framepart containing message data, differently from a header part of ageneral communication system.

If the incremental redundancy (IR) HARQ scheme is also used as theretransmission scheme, the grant message may further include theabove-mentioned IR version information for data retransmission. The IRHARQ scheme from among various HARQ schemes performs channel encoding ofinformation data to improve a data reception (Rx) performance, andtransmits different coding bits whenever the retransmission isoperatedoperated.

The IR version information is associated with the number ofretransmission times of the synchronous HARQ scheme, so that thetransmission/reception end can tacitly recognize the IR versioninformation. That is, in the case of using the synchronous HARQ scheme,the first IR version is used for a first transmission, a second IRversion is used for a second retransmission, and a third IR version isused for a third retransmission, so that the number of retransmissiontimes can be recognized by the IR version information.

The Node-B receives data from the UE at the timing TTI=1, and determineswhether retransmission of the data is required or not. If the dataretransmission is no longer required, the Node-B transmits the ACKsignal to the UE. Otherwise, if the data retransmission is required, theNode-B transmits the NACK signal to the UE.

Referring to FIG. 3, the Node-B transmits the NACK signal. It is assumedthat the synchronous channel-non-adaptive HARQ scheme is used, so that areception (Rx) UE can perform data retransmission although the Node-Bdoes not transmit additional retransmission scheduling information whentransmitting the NACK signal.

If the UE receives the NACK signal from the Node-B, it retransmits thedata, which has been transmitted at the timing TTI=1, according to thesecond HARQ process at the timing TTI=5. In this case, as previouslystated above, the UE retransmits data using resource blocks which havethe same size and location information as those of the previous resourceblocks used for the first transmission.

The Node-B receiving the retransmitted (ReTx) data determines whetherretransmission of the ReTx data is also required or not. As can be seenfrom FIG. 3, the Node-B transmits the NACK signal to the above-mentionedReTx data.

In this case, the base station according to the above-mentionedembodiment may change the retransmission scheduling to another. If theNode-B transmits the NACK signal to the UE so as to requestretransmission of data, the Node-B performs scheduling so that the datacan be retransmitted using other transmission blocks during theretransmission according to the scheduling information. Then, the Node-Binforms the UE of the changed scheduling information.

In brief, the synchronous channel-non-adaptive HARQ scheme is basicallymaintained, however, the retransmission timing information, the RB usedfor the retransmission, or the transmission scheme is changed toanother, so that the system flexibility increases.

If the retransmission scheduling is changed to another according to theabove-mentioned embodiment, the Node-B informs the UE of the changedscheduling information. The UE receives the NACK signal and the changedscheduling information from the Node-B, so that it will retransmit dataaccording to the newly-received changed scheduling information, insteadof the predetermined retransmission scheme.

According to this embodiment of the present invention, although datatransmission is operatedoperated by the synchronous channel-non-adaptiveHARQ scheme, the RB size and location information, the retransmissiontiming information, or the transmission scheme can be adaptively changedto others.

A method for retransmitting data by changing the RB used for theretransmission will hereinafter be described.

In FIG. 3, provided that the UE transmits data using the A resourceblock during the initial transmission and the first retransmission, theNode-B performs scheduling so that the data can be transmitted using theB resource block, instead of the A resource block, at the secondretransmission timing according to the scheduling information. And, theNode-B informs the UE of information of the B resource block, so thatthe UE can transmit data using the B resource block at the secondretransmission timing.

Therefore, in this case, differently from the typical synchronouschannel-non-adaptive HARQ scheme designed to transmit the NACK signalwithout any retransmission scheduling information, the Node-B transmitsretransmission scheduling information of the changed resource block(s)to the UE, so that the UE performs data retransmission over the Bresource block.

A variety of methods may be used to transmit the changed schedulinginformation. A message format capable of transmitting the changedscheduling information is newly defined, so that data can be transmittedover a control channel. Also, a conventional message format may beextended or modified as necessary, so that the convenience messageformat may also be used to transmit the changed scheduling information.For example, the change scheduling information may be transmitted overthe above-mentioned grant message.

In the case of using the above-mentioned embodiment, if the Node-B musttransmit data to another UE via the retransmission timing and thecorresponding resource block (RB), or must transmit other data of thecorresponding UE, the collision problem between Tx data units can besolved.

FIG. 4 is a conceptual diagram illustrating a retransmission method foruse in a multi-carrier system according to the present invention.

FIG. 4 shows a method for indicating whether data is retransmitted usinga scheduling message (e.g., a grant message) on the condition of uplinkdata transmission.

In this way, in the case where the Node-B transmits information of thechanged resource block using the scheduling message, the schedulingmessage for the retransmission includes specific informationcorresponding to the NACK signal, so that there is no need toadditionally transmit the NACK signal. According to the above-mentionedembodiment of FIG. 4, it will be obvious to those skilled in the artthat the embodiment of FIG. 3 can also be applied to the embodiment ofFIG. 4 as necessary.

Similar to the embodiment of FIG. 3, the embodiment of FIG. 4 alsoassumes that the UE retransmits data via the second HARQ process in the4-channel HARQ system, a first data is transmitted at TTI=1, and thedata cannot be retransmitted at TTI=9 in the synchronouschannel-non-adaptive HARQ scheme based multi-carrier system.

According to the above-mentioned embodiment of FIG. 4, the Node-B maytransmit a grant message instead of the NACK signal. Although FIG. 4shows a method for indicating a reception acknowledgement using both theACK/NACK signal and the grant message, the grant message instead of theACK/NACK signal of FIG. 4 can be transmitted, so that the grant messagecan replace the ACK/NACK signal function.

Although the synchronous channel-non-adaptive HARQ scheme is applied tothe embodiment of FIG. 4 in the same manner as in FIG. 3, dataretransmission can be operated on the basis of the changed schedulinginformation. Specifically, the changed scheduling information istransmitted via the grant message according to the embodiment of FIG. 4,so that the embodiment of FIG. 4 can be more easily implemented.

If the Node-B informs the UE of the changed scheduling information viathe grant message, the MCS and information associated with othertransmission schemes transmittable by the grant message can betransmitted in the same manner as in the initial transmission. Needlessto say, the RB location, the number of used RBs, and the MCS level maybe changed and transmitted. In this case, the MCS level is pre-definedbetween the Node-B and the UE according to the payload size of Tx dataand the number of RBs.

In this way, in order to request the UE to retransmit data using thegrant message, it is preferable that the grant message transmitted fromthe Node-B may indicate whether new data transmission is requested orretransmission is requested.

An exemplary method for allowing the UE to recognize which one of thenew data transmission and the retransmission is requested by the Node-Bwill hereinafter be described in detail.

FIG. 5 is a conceptual diagram illustrating a method for informing thata grant message indicating which one of new data transmission andretransmission is requested in case that the grant message is used forrequesting retransmission according to another embodiment of the presentinvention.

The embodiment of FIG. 5 adds an information bit composed of one or morebits as transmission type indication information, and indicates whichone of the new data transmission and the retransmission is requested bythe grant message using the added information bit. According to thepresent invention, the transmission type indication information isreferred to as an NIB (New data Indicator Bit) composed of 1 bit.

For example, if the grant message indicates the new data transmission asshown in FIG. 5, the NIB is set to “0”, and then the grant message istransmitted with the NIB of “0”. If the grant message indicates theretransmission as shown in FIG. 5, the NIB is set to “1”, and then thegrant message is transmitted with the NIB of “1”. In other words, the UEreceiving the grant message checks the NIB value, so that it candetermine which one of the new data transmission and the retransmissionis indicated by the grant message on the basis of the checked NIB value.

In the meantime, an unexpected error occurs in reception of the grantmessage indicating the new data transmission, so that the UE may beunable to recognize which one of the new data transmission and theretransmission is indicated by the following grant message indicatingthe retransmission.

For example, although the Node-B transmits the grant message indicatingthe retransmission to the UE, the UE erroneously decodes the NACK signalof the previous Tx timing, so that it is unable to recognize whether theNode-B has transmitted the first grant message indicating theretransmission or has erroneously received the second grant messageindicating the new data transmission.

A variety of retransmission methods in which the reception error of thegrant message is considered will hereinafter be described in detail.

FIG. 6 is a conceptual diagram illustrating a method for informing thata grant message indicating which one of new data transmission andretransmission is requested in case that the grant message is used forrequesting retransmission according to another embodiment of the presentinvention.

The embodiment of FIG. 6 includes transmission type indicationinformation, and indicates which one of the new data transmission andthe retransmission is requested by the grant message using thetransmission type indication information. In this case, the togglingscheme for changing the value in a predetermined case is applied thetransmission type indication information. As a result, the embodiment ofFIG. 6 prepares against the reception error of the grant message. InFIG. 6, the transmission type indication information is also called“NIB” (New data Indicator Bit), and it is assumed that the NIB iscomposed of 1 bit.

For example, if the grant message indicates the new data transmission asshown in FIG. 6, the NIB value may be changed to another value. The NIBvalue is set to “1” (i.e., NIB=1) as a grant message for indicating thenew data transmission to specific data “Data1”.

Then, if the grant message indicates the new data transmission toanother data “Data2”, the NIB value is toggled to set to “0” (i.e.,NIB=0) by the toggling scheme.

In the case where the grant message indicating the retransmission isapplied to the UE at the next retransmission timing, the value of NIB=0remains unchanged, so that the UE can recognize the occurrence of theretransmission to the data “data2”. In other words, the NIB value ischanged only when the grant message indicating the new datatransmission.

The UE receives the grant message, and determines whether the NIB valueof the received grant message is different from another NIB valuereceived in a previous HARQ process. If the NIB value of the receivedgrant message is different from the other NIB value received in theprevious HARQ process, this means that the grant message indicates thenew data transmission, so that the UE deletes all of data from thebuffer and transmits new data packet.

And, if the NIB value of the grant message received in the UE is equalto the other NIB value received in the previous HARQ process, this meansthat the grant message indicates the retransmission, so that the UEretransmits the data packet stored in the buffer.

As can be seen from FIG. 6, the UE may unexpectedly miss the grantmessage indicating the new data transmission. If a channel is in a deepfading status, the Node-B may detect only energy of a very low level. Inthis case, the Node-B transmits the grant message indicating theretransmission.

If the Node-B transmits the grant message according to the embodiment ofFIG. 5, and the UE misses the grant message, the above-mentioned UE mayretransmit data to another data “Data1” instead of “Data2”. However, ifthe toggling scheme is applied to the NIB value according to the presentinvention, the above-mentioned problem can be solved.

For example, if the UE receives the first grant message indicatingtransmission of “Data2”, the UE compares the NIB value of the grantmessage indicating the retransmission of “data2” with the NIB value ofthe previous grant message, confirms that the two NIB values are equalto each other, and performs retransmission of “data2” stored in thebuffer.

If the UE does not receive the initial grant message indicating thetransmission of “data2”, the UE compares the NIB value of the grantmessage indicating retransmission of “data2” with the other NIB value ofa previous grant message, confirms that there is a difference betweenthe two NIB values, deletes “data1” stored in the buffer, and begins toperform initial transmission of “data2”. Namely, from the viewpoint ofthe UE, the above-mentioned operation is considered to be the initialtransmission, however, from the viewpoint of the Node-B, theabove-mentioned operation is considered to be reception ofretransmission data.

FIG. 7 is a conceptual diagram illustrating a method for informing thata grant message indicating which one of new data transmission andretransmission is requested in case that the grant message is used forrequesting retransmission according to another embodiment of the presentinvention.

The embodiment of FIG. 7 adds an information bit composed of one or morebits as sequence number information, and indicates which one of the newdata transmission and the retransmission is requested by the grantmessage using the added information bit. According to the presentinvention, the sequence number information is referred to as a sequencenumber (SN).

If the SN is added to the grant message and then the UE receives theresultant grant message including, the SN, the UE can recognize whichone of the new data transmission and the retransmission is requested bythe grant message, and can also recognize what one of data isretransmission-requested for by the grant message. A method forestablishing the SN value according to the present invention is asfollows.

The SN information is transmitted along with the grant message, or iscontained in the grant message and is then transmitted, withoutdistinguishing between the new data transmission and the retransmission.Whenever the Node-B receives a retransmission request of the same datapacket, the SN value increases by “1”. If the new data transmission isrequested, the SN value is initialized to be an initial value.

For example, it is assumed that the SN initial value is set to “0”. Inother words, in the case of transmitting the grant message indicatingthe new data transmission, the SN value is set to “0”. Therefore, if theSN value transmitted along with the grant message is not equal to thevalue of “0”, the UE can recognize that the above-mentioned grantmessage indicates the retransmission.

Referring to FIG. 7, if the UE receives the grant message and the SNvalue of the received grant message is equal to “2”, the UE performsretransmission of the initially-transmitted data before 8 sub-framesdenoted by (2(SN)*4(HARQ channel)=8).

However, provided that the SN value is not equal to “0” at a time atwhich the grant message is received, and at the same time is not equalto the other SN value, which should be received in association withcurrent retransmitting data, i.e., provided that the just-before grantmessage is missed, the UE deletes all of data stored in the bufferwithout retransmitting data of the previously-received grant message,and begins to perform the initial transmission of new data.

In more detail, as can be seen from FIG. 7, if the UE misses or losesthe grant message indicating the initial transmission of “data2”, or ifthe UE detects energy of a very low level due to a deep-fading channelalthough data has been transmitted, the Node-B transmits a messageindicating the retransmission along with the signal of SN=1.

In this case, if the UE has not missed the previous grant message, itcan be recognized that the SN value, which should be received inassociation with the current retransmission data, is not equal to “2”.Therefore, since the SN=0 status is not established, the UE deletes allof data associated with “data1” from the buffer and performsretransmission of “data2”, instead of performing retransmission of“data1”

The “data2” instantaneous transmission operated by the UE may beconsidered to be the retransmission request from the viewpoint of theNode-B. However, if the UE has previously missed the grant messageindicating the initial transmission of “data2”, this means that theinitial transmission of “data2” is operated from the viewpoint of theUE. As a result, the UE may not wrongly recognize the retransmissiondata packet.

FIG. 8 is a conceptual diagram illustrating a method for indicating aretransmission stop according to an embodiment of the present invention.

The embodiment of FIG. 8 assumes that the synchronouschannel-non-adaptive HARQ scheme and the second HARQ process are used inthe same manner as in FIGS. 3 and 4.

In order to request the UE to stop the retransmission, the Node-B mayexemplarily use a stop message, and a detailed description thereof willhereinafter be described.

Referring to FIG. 8, the Node-B transmits the grant message to the UE,so that it requests the UE to transmit data. The UE checks the receivedgrant message, and performs uplink data transmission at the timingTTI=1.

The Node-B checks the data transmitted from the UE. If retransmission ofthe data is required, the Node-B transmits the NACK signal to the UE.Upon receiving the NACK signal from the Node-B, the UE performsretransmission of the data at a predetermined timing according to thesynchronous channel-non-adaptive HARQ scheme at TTI=5.

According to this embodiment of the present invention, the Node-Btransmits the stop message to the UE, so that it may stop the UE'sretransmission at the next retransmission timing based on thesynchronous non-adaptive HARQ scheme. The UE receiving the stop messagedoes not perform retransmission at a predetermined timing TTI=9, doesnot delete data, having been transmitted at a previous timing, from thebuffer, and keeps the above-mentioned data in the buffer. The UEreceiving the stop message does not perform retransmission for apredetermined time, and does not delete data from the buffer. In thiscase, the predetermined time may be equal to two times the establishretransmission interval, or may be set to a time consumed until the UEreceives specific information indicating either the new datatransmission or the retransmission from the Node-B.

Another method for requesting the UE to stop the retransmission may be amethod for employing the above-mentioned grant message.

The Node-B transmits information indicating no allocation RB to the UEvia the grant message, so that it may request the UE to stop theretransmission in the synchronous channel-non-adaptive HARQ system. Forexample, when transmitting the number of RBs contained in the grantmessage or the RB size information contained in the same grant message,the Node-B may include information of “0” in the transmittedinformation.

If the Node-B stops the retransmission at the UE's reservedretransmission timing, then the Node-B may request retransmission viathe same HARQ process as that of the initial transmission. The Node-Bre-allocates resource blocks (RBs) at the next retransmission timingcorresponding to the same HARQ process, and transmits the RB informationvia the grant message indicating the retransmission, so thatretransmission of corresponding data can be restated.

Thereafter, the Node-B transmits the NACK signal requesting theretransmission to the UE, so that the UE retransmits thepreviously-transmitted data stored in the buffer at the nextretransmission timing point TTI=13.

In the meantime, if the UE receiving the stop message may receive theACK signal from the Node-B within a predetermined time, or may notreceive the ACK signal within the predetermined time, it deletes datastored in the buffer, and may be ready to transmit new data.

In this case, if there is no resource block to be allocated for theretransmission at the reserved retransmission because of other datatransmitting, the UE stops the retransmission for a little while,retransmission can be more flexibly scheduled.

FIG. 9 is a conceptual diagram illustrating a method for indicating aretransmission according to an embodiment of the present invention.

The embodiment of FIG. 9 discloses a method for performing theretransmission using a retransmission message. In this case of theembodiment of FIG. 9 it assumed that the synchronous non-adaptive HARQscheme is basically applied to the above-mentioned method, and thesecond HARQ process is also applied to the above-mentioned method, sothat the resultant data is retransmitted at a corresponding timing.

Differently from the above-mentioned embodiments, the embodiment of FIG.9 allows the Node-B to use a retransmission (ReTx) message to indicatethe retransmission, and allows the Node-B to use the stop message tostop the retransmission in such a way that the retransmission process isoperated. The ReTx message and the stop message are not limited to theabove-mentioned terms, and can also be replaced with other terms asnecessary.

The stop message of FIG. 9 is designed to perform the same function asthe stop message of FIG. 8. The stop message of FIG. 9 does notretransmit the previously-transmitted data, however, it requests the UEto maintain data in the buffer.

The Node-B transmits a grant message for the new data transmission tothe selected UE. The UE checks the grant message, and performs uplinktransmission at TTI=1. If the Node-B checks data transmitted from the UEand determines the necessity of retransmission, and transmits the ReTxmessage for requesting the retransmission to the UE.

The UE receiving the ReTx message performs retransmission of thepreviously-transmitted data. The stop message of FIG. 9 is equal to thatof FIG. 8, so that its detailed description will herein be omitted forthe convenience of description.

Differently from FIG. 8, the embodiment of FIG. 9 allows the Node-B totransmit the grant message indicating the retransmission, so that theretransmission interrupted by the stop message is initiated as well asthe ReTx message.

In more detail, under the condition that the UE does not delete datafrom the buffer by receiving the stop message and does not perform theretransmission at predetermined retransmission timing due to the stopmessage, if the above-mentioned UE receives the grant message indicatingthe retransmission, data kept in the buffer is retransmitted at TTI=13.

In this case, if the UE receives the other grant message indicating thenew data transmission instead of the retransmission, it resets thebuffer, deletes data kept in the buffer, stores new data in the buffer,so that it may transmit the new data to the Node-B.

Under the above-mentioned situation, there are two statuses, i.e., theretransmission status and the retransmission stop status, so that theNode-B can inform the UE whether the Node-B would retransmit data orwould stop transmission of the data using a single bit. In other words,the Node-B informs the UE of the retransmission using the ReTx message,and informs the UE of the retransmission resumption using the stopmessage.

If the received (Rx) packet is unsuccessfully demodulated, the Node-Btransmits the ReTx message to the UE. However, if the Node-B desires totemporarily stop transmission of data applied to the UE at apredetermined retransmission timing irrespective of the success orfailure of the demodulation, the Node-B transmits the stop message tothe UE.

When the UE receives the stop message from the Node-B, it cannotimmediately recognize whether the received stop message is caused by thesuccess of reception, and cannot recognize whether the received stopmessage aims to temporarily prevent the data from being transmitted tothe Node-B at a specific timing point.

The UE stores data in the buffer for a predetermined time. If theabove-mentioned UE receives the grant message indicating theretransmission from the Node-B, it retransmits the data stored in thebuffer to the Node-B. Otherwise, if the above-mentioned UE receives theother grant message indicating the new data transmission from theNode-B, the UE recognizes that the data stored in the buffer has beensuccessfully received, so that it makes the buffer empty.

Although the grant message indicating the new data transmission is nottransmitted from the Node-B, if the retransmission (RxTx) message is nottransmitted from the Node-B for a predetermined time, the UE may deletethe transmitted (Tx) data from the buffer.

As described above, the incremental redundancy (IR) HARQ scheme can beused for the HARQ scheme. If the synchronous non-adaptive HARQ schemeemploying the stop message and the IR version management scheme arecombined with each other according to this embodiment, themisunderstanding of the IR version, corresponding to the retransmissionaction caused by the ReTx grant message located after the stop message,may occur.

While the UE receives the message and attempts to perform theretransmission using the received message, the Rx error of thepreviously-transmitted stop message may occur. As a result, there arisesthe misunderstanding of information indicating how many retransmissionsare between the UE and the Node-B. Namely, there arises themisunderstanding of information indicating which one of IR versions isapplied to the retransmission, so that data reception may be abnormallyoperated.

Therefore, if the Node-B transmits the grant message indicating theadditional retransmission, the above-mentioned embodiment designates theIR version used for ReTx data, and transmits the RxTx data using thedesignated IR version.

In this case, there is no change in the grant message indicating theretransmission, from among some field areas contained in the other grantmessage indicating the new data transmission using the synchronousnon-adaptive HARQ scheme, so that some fields may not request the setupprocess. If the Node-B transmits the IR version information using theabove-mentioned fields in which the setup process is no longer required,it can transmit the IR version information without adding a new field tothe grant message.

For example, there is no change in payload size of Tx data based on thesynchronous HARQ scheme, thus, if a payload field of the grant messageindicating the new data transmission is transmitted as a ReTx grantmessage, the payload field is used as a field of information designatingIR version. Therefore, although the retransmission is operated after theNode-B transmits the stop message, the correct IR version can beindicated, so that there could be no misunderstanding on the IR version.

For another example, a method for resetting the IR version value to apredetermined value during the retransmission can be used. In otherwords, this method does not set the actual IR version value inconsideration of the previous retransmission, but sets a predeterminedvalue. Thus, if the Node-B transmits the grant message indicating theretransmission after transmitting the stop message, the above-mentionedmethod resets the IR version value to the predetermined value, andtransmits the resultant IR version value to a corresponding UE.

In this case, the Node-B can inform the UE of the reset IR versioninformation using some fields, which are contained in the grant messageindicating the new data transmission, without defining a new field.

FIG. 10 is a conceptual diagram illustrating a method for transmitting aretransmission request message according to an embodiment of the presentinvention.

The embodiment of FIG. 10 shows a method for retransmitting data bychanging a retransmission timing in the synchronous non-adaptive HARQscheme based multi-carrier system. In order to allow the UE to performretransmission of data, it is assumed that the second HARQ process isapplied to the embodiment of FIG. 10.

Referring to FIG. 10, the Node-B selects a UE which will perform uplinktransmission, and transmits the grant message to the selected UE. The UEreceives the grant message, and performs uplink transmission of dataaccording to corresponding scheduling information at TTI=1.

The Node-B receives Tx data from the UE. If the Node-B determines thatthe Tx data should be retransmitted from the UE, it transmit theACK/NACK signal to the UE, so that the UE can recognize the presence orabsence of a retransmission request.

It is assumed that the multi-carrier system in the above-mentionedembodiment of FIG. 10 employs the synchronous channel-non-adaptive HARQscheme. If the UE receives the NACK signal from the Node-B, itretransmits the data at a predetermined timing TTI=5. Then, ifretransmission of the data is required again, the Node-B transmits theNACK signal so that it requests the UE to perform the retransmission. Inthis case, the NACK signal is retransmitted at a predetermined timingTTI=9.

However, this embodiment of FIG. 10 provides a method for changing aretransmission timing. In more detail, the Node-B cannot performretransmission using the resource blocks (RBs), having been used for theignition transmission, at a pre-engaged timing TTI=9, so that the Node-Brequests the UE to perform the retransmission at another timing TTI=10.Thus, the Node-B transmits information of the changed timing to the UE,and the UE performs the retransmission at the changed timing.

In the case of the synchronous HARQ-based system, the timing point, atwhich the ACK/NACK signal, the ReTx/Stop message, or the grant messageis received, is correlated with the other timing point at which data isretransmitted as a response to each signal. In this way, theretransmission timing point can be changed to another as necessary.

For example, in the case of using the grant message indicating theretransmission, the Node-B transmits the grant message to the UE at aspecific timing (at which the retransmission can be executed) of thethird HARQ process timing. In this case, the above-mentioned grantmessage must include information indicating that thecurrently-transmitted ReTx grant message requests retransmission of dataassociated with the third HARQ process instead of the second HARQprocess.

In order to perform the initial transmission and the firstretransmission, the UE transmits data using the second HARQ process atcorresponding timing intervals TTI=1 and TTI=5. However, during thesecond retransmission, the UE transmits data at the third HARQ processtiming. After receiving the ReTx grant message including the changedHARQ process information, in order to reply to the ReTx grant message,the UE retransmits the data, which has been transmitted at the firstHARQ process, at the timing TTI=10 corresponding to the third HARQprocess.

If transmission of high-priority data is requested by a correspondingresource block (RB) of a predetermined timing, and the UE has difficultyin performing the retransmission using the predetermined timing and RBinformation, the above-mentioned operation enables the UE to effectivelycommunicate with the Node-B.

FIG. 11 is a conceptual diagram illustrating a method for simultaneouslyemploying the retransmission stop request message and the retransmissionrequest message according to an embodiment of the present invention.

The embodiment of FIG. 11 provides a method for more effectivelyperforming the embodiment of FIG. 10 designed to change theretransmission timing, using the stop message. According to thisembodiment of FIG. 11, if the retransmission timing desired to bechanged is later than the original scheduling timing, the embodiment ofFIG. 11 transmits the stop message at the original retransmissiontiming.

In FIG. 11, if the Node-B performing scheduling cannot allocate thecorresponding resource block (RB) to the originally-scheduled UE at thetiming TTI=9, the Node-B transmits the stop message to reserve theretransmission to be performed at the timing TTI=9. In this case,although the stop message does not request the UE to perform theretransmission, this stop message enables the UE not to deletecorresponding data from the buffer, so that the data is kept in thebuffer, as previously stated above.

The Node-B transmits the grant message for requesting the UE to performthe retransmission at the timing TTI=10 used as a retransmissionindication timing. In this case, specific information, indicating thatretransmission of the data having been transmitted to the second HARQprocess is requested, is included in the above-mentioned grant message,so that the UE can correctly recognize which one of data isretransmission-requested by the Node-B.

If the above-mentioned specific information, indicating thatretransmission associated with the second HARQ process is requested, isnot included in the aforementioned grant message, the UE recognizes thatretransmission associated with the third HARQ process is requested atthe timing TTI=10 according to the original setup status, so that it hasdifficulty in implementing a desired effect.

If the retransmission timing is changed as described above, the Node-Bis unable to provide the UE with correct information indicating whetherdata will be transmitted at the predetermined timing. So, if the UE doesnot receive a retransmission request signal at a predetermined timing,it may wrongly decide whether or not to delete data from the buffer.

However, if the Node-B according to the above-mentioned embodiment ofFIG. 11 informs the UE of the stop message, so that it prevents data ofthe UE from being retransmitted at the predetermined timing. And,resulting in the implementation of no collision between the second HARQprocess data and the third HARQ process data can be expected. In brief,a data retransmission method for changing a transmission timing (i.e.,HARQ process) using the synchronous HARQ-based scheme can be moreeffectively performed.

Compared with the method for scheduling the retransmission timing usingthe stop message, the above-mentioned method of FIG. 11 is superior tothe above-mentioned method for scheduling the retransmission method.

Namely, in order to maintain the synchronous non-adaptive HARQcharacteristics, the UE must retransmit data according to aretransmission timing based on the second HARQ process. If the data isnot retransmitted at the timing TTI=9, the UE must wait for the nextretransmission timing TTI=13. However, a method for changingtransmission process (i.e., retransmission timing) is also used, so thatthe data can be retransmitted at the timing TTI=10, resulting in no Txtime delay.

If the Node-B desires to change the ReTx timing to another as describedin FIGS. 10 and 11, it is preferable that the Node-B must determinewhich one of data is retransmission-requested, and must inform the UE ofthe determined result. In order to retransmit the changed ReTxinformation, the Node-B may inform the UE of the original HARQ processinformation of data to be retransmitted at the timing TTI=10.

In this way, in order to inform the UE of the HARQ process information,a new message format is defined and used. If the Node-B transmits thegrant message indicating the retransmission, it may transmit the HARQprocess information using a specific field from among fields containedin the grant message. In this case, the specific field has no need to bechanged during the retransmission.

For example, in the case of the grant message for transmitting new dataand the ReTx grant message, there is no change in the payload size of Txdata, so that a field indicating the payload of the message for the newdata transmission may be used as the HARQ process indication field.

For another example, in the case of using the grant message indicatingthe retransmission, a field for indicating the changed HARQ processinformation in the grant message may be added to the above-mentionedgrant message as necessary. By the grant message indicating theretransmission, there is a change in the HARQ process during theretransmission. This HARQ process change can be provided on theassumption that the UE would not normally receive the above-mentionedretransmission grant message. Therefore, if the UE does not receive theReTx grant message, an unexpected error may occur in overall operations.Therefore, the field indicating the HARQ process information is added tothe above-mentioned grant message, so that the Node-B may allocate theHARQ process information to a resource allocation point for the new datatransmission, irrespective of the Tx timing.

If the retransmission is operated by the above-mentioned HARQ scheme,the reception end may have two kinds of errors (i.e., ACK-to-HACK errorand NACK-to-ACK error) when receiving the ACK/HACK signal.

The ACK-to-NACK error indicates a UE's erroneous decoding operation, inwhich the UE decodes the ACK signal into the NACK signal due to achannel status or other factors although the Node-B has transmitted theACK signal to reply to Tx data of a transmission end (e.g., UE).

The NACK-to-ACK error indicates that the UE decodes the NACK signal intothe ACK signal due to a channel status or other factors although theNode-B has transmitted the NACK signal for requesting the retransmissionupon receiving Tx data from the UE.

Operation schemes for employing the above-mentioned embodiments when theNACK-to-ACK error occurs will hereinafter be described.

FIG. 12 is a conceptual diagram illustrating a general NACK-to-ACKerror.

Referring to FIG. 12, the Node-B transmits the NACK message afterreceiving data from the UE, and waits for the UE to retransmit the data.However, if the NACK-to-ACK error occurs, the UE does not wait for theretransmission any longer, and deletes all of data stored in the buffer.

According to the HARQ scheme based on the ACK/NACK signal, although theNode-B waits for retransmitted data from the UE, the UE does nottransmit data any longer, so that a time-frequency area is wasted by apredetermined amount corresponding to the maximum number of ReTx times.

The Node-B detects energy using the HARQ scheme, and determines thepresence or absence of any error in the ACK/NACK signal using the HARQscheme. Specifically, the Node-B can determine whether the NACK-to-ACKerror occurs. Namely, the Node-B determines that the transmission end(e.g., UE) has not transmitted data to the Node-B on the basis of thedetected energy, or determines whether an error has occurred althoughdata has been normally transmitted to the Node-B on the basis of thedetected energy.

FIG. 13 is a conceptual diagram illustrating an exemplary method forapplying an embodiment of the present invention in consideration of theACK/NACK error.

If the Node-B detects the NACK-to-ACK error, the embodiment of FIG. 13provides a new scheduling method for transmitting the UE's new data ornew UE's data.

If the Node-B determines the occurrence of the NACK-to-ACK error bydetecting the energy, this situation may occur because the UE may nottransmit actual data to the Node-B, or may also occur because the UE isin the deep fading status.

If it is determined that the UE was in the deep fading status, theNode-B may prefer to schedule other frequency bands, instead ofrequesting the retransmission from the UE. Therefore, if the NACK-to-ACKerror occurs, the Node-B terminates the prior data retransmissionprocess without requesting the retransmission from the UE, and thenperforms new scheduling of the next UE where data will be transmitted.In this case, retransmission of the prior data can be operated by anupper layer.

Referring to FIG. 13, a first UE (UE1) receives the grant message fromthe Node-B, and transmits uplink data to the Node-B. In order to commandthe UE1 to retransmit the data, the Node-B transmits the NACK signal tothe UE1.

However, the UE1 mistakes the NACK signal for the ACK signal althoughthe Node-B has transmitted the NACK signal. Thus, the UE1 does notretransmit the data, and the Node-B detects that a reception (Rx) signalhas a weak strength at a specific time at which retransmission data willbe received, so that the Node-B detects the occurrence of theNACK-to-ACK error.

Although there is no NACK-to-ACK error (i.e., the UE1 has retransmitteddata), the Node-B may mistake the normal operation for the NACK-to-ACKerror. In more detail, because the UE1 is in the deep fading status, theNode-B may not receive UE1′s retransmission data or may not decode theUE1′s retransmission data.

If the NACK-to-ACK error is detected by the Node-B, the retransmissionresources pre-scheduled by the synchronous HARQ scheme are used as theUE's new data or scheduling resources of other UEs.

As can be seen from FIG. 13, the Node-B newly allocates resourcesreserved for the UE1′s retransmission to implement data transmission ofa second UE (UE2).

If the grant message indicating the aforementioned resources istransmitted to the UE2, the UE2 receives the grant message and transmitsuplink data.

Although the Node-B can detect the presence or absence of theNACK-to-ACK error using the above -mentioned method, it cannot preventthe resources from being wasted using only the conventional ACK/NACKoperation scheme. As soon as the UE receives the ACK signal, the UEmakes its own retransmission buffer empty, so that the UE has no moredata to be retransmitted although the Node-B retransmits the NACK signalin order to request retransmission from the UE.

FIG. 14 is a conceptual diagram illustrating another exemplary methodfor applying an embodiment of the present invention in consideration ofthe ACK/NACK error.

The embodiment of FIG. 14 provides a method for maintaining Tx data of atransmission end in the buffer during a predetermined time, withoutdeleting the Tx data from the buffer, although the transmission end doesnot retransmit data upon receiving the ACK signal from the receptionend.

The above-mentioned embodiment of FIG. 14 is similar to functions of thestop message. Namely, this embodiment may be similar to the otherembodiment for transmitting the ACK signal used as the stop message. TheUE receiving the ACK signal does not retransmit data as if the UE hasreceived the stop message, however, and the previously-transmitted datastored in the buffer is maintained for a predetermined time.

For example, according to the uplink transmission, when receiving theACK signal from the Node-B, the UE stores retransmission data of in thebuffer during a predetermined time without any change, instead ofdeleting all of data stored in the buffer. Then, if the UE receivesagain the NACK signal from the Node-B, it immediately retransmits thedata stored in the buffer to the Node-B, so that resources are notunnecessarily consumed. In this case, the predetermined time for storingthe data may be equal to a time reaching the next retransmission atleast.

FIG. 15 is a conceptual diagram illustrating still another exemplarymethod for applying an embodiment of the present invention inconsideration of the ACK/HACK error.

The embodiment of FIG. 15 provides a method for maintaining Tx data ofthe transmission end in the buffer without deleting the Tx data from thebuffer, although the transmission end does not retransmit data uponreceiving the ACK signal from the reception end. But, if the ACK/NACKerror occurs in the reception end, the embodiment of FIG. 15 provides amethod for transmitting the scheduling message.

According to the embodiment of FIG. 15, although the transmission endreceives the ACK signal, it continuously stores data in the buffer untilreceiving a scheduling message for indicating the new data transmissionor the retransmission.

The transmission end continuously stores data in the buffer untilreceiving the scheduling message from the reception end. And, as soon asthe transmission end receives the scheduling message indicating the newdata transmission from the reception end, it deletes all of data storedin the buffer.

In the uplink transmission, the NACK-to-ACK error occurs, the Node-Bconfirms the presence of the NACK-to-ACK error by detecting energy, andperforms new scheduling as shown in FIG. 13. In this case, under thecondition that previous or old data has not been successfully received,the Node-B transmits data to another IE or transmits another data,resulting in an increased FER. Thus, this embodiment of FIG. 15transmits a scheduling message after detecting the NACK-to-ACK error, sothat the Node-B can transmit ReTx data to the erroneous UE usingdifferent frequency areas.

This embodiment of FIG. 15 may also be used as a method for allowing theUE to determine the presence or absence of the ACK/NACK error. The UEtransmits data, receives the ACK/NACK signal of the data, and determinesthe presence or absence of the ACK/NACK error by referring to thescheduling message received after the ACK/NACK signal.

The UE is able to determine whether the retransmission is operated atthe reception time of the ACK/NACK signal. However, the UE does notfinally determine the success or failure of data transmission using onlythe ACK/NACK signal, determines the presence or absence of errors of theACK/NACK signal by referring to the scheduling message, and decideswhether or not to delete data from the buffer by referring to thescheduling message.

For example, if it is determined that the UE receives the ACK signal,the UE does not retransmit data at the retransmission timing, andcontinuously maintains the data in the buffer at the same retransmissiontiming.

Thereafter, if the UE receives the grant message indicating the new datatransmission, it deletes the data from the buffer, and transmits the newdata. Under this situation, it is considered that the above-mentionedACK signal received in the UE has no error. Otherwise, if the UEreceives the grant message indicating the retransmission from theNode-B, it retransmits the data stored in the buffer. Under thissituation, it is considered that the above-mentioned ACK signal receivedin the UE has errors.

In the meantime, if the Node-B transmits a scheduling message (e.g., thegrant message indicating the retransmission) to the UE, operations ofthe Node-B and the UE may be equal or similar to those of the method ofFIG. 4. The retransmission is operated by the grant message, so thatonly the locations of used resource blocks (RBs) are changed to otherlocations, but the MCS level or other components may be equal to thoseof the initial transmission. Otherwise, all of the RB location, thenumber of used RBs, and the MCS level may also be changed to others. Inthis case, the MCS level may be pre-defined between the Node-B and theUE on the basis of the payload size of Tx data and the number of usedRBs.

A method for determining which one of the new data transmission and theretransmission is indicated by the grant message shown in FIG. 15 may beequal or similar to those of the methods of FIGS. 5-7.

In this case, the grant message includes the ACK/NACK information, sothat there is no need to additionally the ACK/NACK information. In moredetail, a reception end of data (e.g., Node-B) may simultaneouslytransmit the ACK/NACK signal and the grant message. However, if theNode-B transmits the grant message, there is no need to transmit theACK/NACK signal. If the UE receives the grant message indicating theretransmission from the Node-B, it disregards the received ACK/NACKsignal, and performs the retransmission via the resource area requestedby the Node-B.

FIG. 16 is a conceptual diagram illustrating a method for controllingretransmission via the ACK/NACK message according to an embodiment ofthe present invention.

The embodiment of FIG. 15 provides a method for continuously storing Txdata in a buffer for a predetermined time although the UE receives theACK signal, so that the Node-B can more effectively schedule resources.After the UE receives the ACK signal, it continuously stores Tx data inthe buffer for the predetermined time.

Thus, although the Node-B has not successfully received the data fromthe UE, it compulsorily transmits the ACK signal so that aretransmission operation of a specific UE can be temporarilyinterrupted. If there is no uplink resource to be allocated to acorresponding retransmission UE at the retransmission timing, thescheduling can be more flexibly operated.

The UE receiving the ACK signal does not retransmit data at acorresponding time, but it does not delete the data from the bufferuntil receiving the grant message. As a result, the Node-B transmits thegrant message indicating the retransmission to the UE at a desired time,so that it restarts retransmission of a corresponding process bytransmitting the grant message indicating the retransmission at adesired time.

The above-mentioned retransmission interruption may also be operated bythe other grant message indicating the retransmission. For example, theRB size of the grant message indicating the retransmission is set to“0”, so that uplink retransmission of the corresponding terminal can betemporarily interrupted. In this case, the Node-B restartsretransmission of a corresponding process by transmitting the grantmessage indicating the retransmission at a desired time.

The present invention can be applied to an uplink of the 1× EV-DOsynchronous system, and can also be applied to an uplink of the 3GPP LTE(Long Term Evolution due to less overhead.

The above-mentioned embodiments of the present invention can beimplemented by hardware, firmware, software, or a combination of them.

In the case of implementing the present invention by hardware, thepresent invention can be implemented with ASICs (application specificintegrated circuit), DSPs (digital signal processors), DSPDs (digitalsignal processing devices), PLDs (programmable logic devices), FPGAs(field programmable gate arrays), a processor, a controller, amicrocontroller, and a microprocessor, etc.

If operations or functions of the present invention are implemented byfirmware or software, the present invention can be implemented in theform of a variety of formats, for example, modules, procedures, andfunctions, etc. The software codes may be stored in a memory unit sothat it can be driven by a process. The memory unit is located inside oroutside of the processor, so that it can communicate with theaforementioned processor via a variety of well-known parts.

It should be noted that most terminology disclosed in the presentinvention is defined in consideration of functions of the presentinvention, and can be differently determined according to intention ofthose skilled in the art or usual practices. Therefore, it is preferablethat the above-mentioned terminology be understood on the basis of allcontents disclosed in the present invention.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

As apparent from the above description, if the retransmission method forthe multi-carrier system is based on a channel-non-adaptiveretransmission scheme, the present invention can flexibly or smoothlyschedule retransmission resources.

If the retransmission method for the multi-carrier system is based on asynchronous retransmission scheme, the present invention can flexibly orsmoothly schedule the retransmission timing point. Also, the presentinvention can more effectively perform the synchronouschannel-non-adaptive HARQ scheme.

The present invention can properly cope with the ACK/NACK errors, sothat a communication performance increases.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A method of data retransmission in a multi carrier system, the methodcomprising: (a) receiving, by a user equipment, a first grant messageincluding a first New Data Indicator (NDI) and first resource allocationinformation for an uplink data transmission, wherein the first NDIindicates whether new data is transmitted or retransmitted; (b)transmitting the uplink data according to the first resource allocationinformation; (c) receiving an acknowledgement message representingwhether the uplink data is successfully received; (d-0) adaptivelyretransmitting the uplink data using second resource allocationinformation when a second grant message, including the second resourceallocation information for the uplink data retransmission and a secondNDI which is not toggled compared with the first NDI, is furtherreceived at the step of (c); and (d-1) non-adaptively retransmitting theuplink data using the first resource allocation information when thesecond grant message is not received and the acknowledgment message is anegative acknowledgement (NACK) message.
 2. The method according toclaim 1, wherein: the first resource allocation information includes afirst transmission timing, a first transmission resource block, a numberof the first transmission resource block, and first MCS (Modulation andCoding Scheme) information; and the second resource allocationinformation includes a second transmission timing, a second transmissionresource block, a number of the second transmission resource block, anda second MCS (Modulation and Coding Scheme) information.
 3. The methodaccording to claim 2, wherein the second grant message further includesredundancy version information for retransmission.
 4. The methodaccording to claim 1, wherein when the acknowledgement message isdetected as a positive acknowledgement message at the step of (c), the(d-0) step further comprising: determining the positive acknowledgementmessage as the negative acknowledgement message when the second grantmessage, including the second NDI which is not toggled compared with thefirst NDI, is received.
 5. The method according to claim 1, wherein avalue of the second NDI is toggled compared to a value of the first NDI,when the second NDI indicates new data transmission.
 6. The methodaccording to claim 4, wherein the second NDI is initialized when thesecond NDI indicates a new data transmission, and the second NDI ischanged according to predetermined rules when the second NDI indicates aretransmission.
 7. A method of data retransmission in a multi carriersystem, the method comprising: (a) transmitting, to a User Equipment(UE), a first grant message including a first New Data Indicator (NDI)and first resource allocation information for an uplink datatransmission, wherein the first NDI indicates whether new data istransmitted or retransmitted; (b) receiving, from the UE, the uplinkdata according to the first resource allocation information; (c)transmitting, to the UE, an acknowledgement message representing whetherthe uplink data is successfully received; (d-0) receiving the uplinkdata which is adaptively retransmitted by the UE using second resourceallocation information when a second grant message, including the secondresource allocation information for the uplink data retransmission and asecond NDI of which value is not toggled compared with a value of thefirst NDI, is further transmitted at the step of (c); and (d-1)receiving the uplink data which is non-adaptively retransmitted by theUE using the first resource allocation information when theacknowledgement message is a negative acknowledgement message.
 8. Themethod according to claim 7, wherein: the first resource allocationinformation includes a first transmission timing, a first transmissionresource block, a number of the first transmission resource block, andfirst MCS (Modulation and Coding Scheme) information; and the secondresource allocation information includes a second transmission timing, asecond transmission resource block, a number of the second transmissionresource block, and second MCS (Modulation and Coding Scheme)information.
 9. The method according to claim 8, wherein the secondgrant message further includes redundancy version information for thedata retransmission.